The invention relates to apparatus for testing the rolling resistance of materials.
For product comparison between competitors, and for researching ways to improve elastomeric products, a means is needed for measuring the rolling resistance of products such as conveyor belts, and elastomeric components such as plies or tread used in pneumatic tires. In the prior art, most apparatus and methods for measuring rolling resistance are directed at measuring components of rolling resistance such as hysteresis, G"", modulus and the like. Using these parameters, an approximation of rolling resistance can be obtained.
The advantage of approximating rolling resistance based on related parameters is that only very small amounts of material are needed to measure the related parameters. The disadvantage is that the measured parameters do not always interact the same way in different materials to provide an accurate estimation of rolling resistance, and there is no way to predict the contribution of the various parameters in a specific product construction, and the approximations are sometimes incorrect by a substantial margin.
Accordingly, it is an object of the present invention to provide a method and apparatus for directly measuring the rolling resistance of a material, especially an elastomeric material, using a relatively small sample of the material.
1. Background Art
At the annual meeting of the Adhesion Society, held, in Savannah, Ga., Feb. 22-25, 1998, Professor M Chaudhury of Leheigh University presented a poster describing research in which an oscillating rubber roller was used to study adhesion on flat surfaces, using the energy expended as the roller rocked backwards and forwards on a chemically-modified flat surface to measure the difference between energy loss in breaking contact and energy gained on making contact.
Rubber covered rollers have been described by M Hannah, Quart.J.Mech.Appl.Math., 4, 95-105 (1951); G. J. Parish, Brit.J.Appl.Phys., 9, 158-161 (1958); G. J. Parish, Brit.J.Appl.Phys., 9, 428-433 (1958); G. J. Parish, Brit.J.Appl.Phys.12,333-335 (1961); M. Barquins and Efelder, Kautschuk u. Gummi 43,no.2, 114-117(1990); F. Zeppernick, Gummi Fasern Kunststoffs 44, 654(1991) to 46,580(1993).
2. Disclosure of Invention
An apparatus for measuring the rolling resistance of a substrate comprises a rolling means for rolling contact with a surface to be measured, an arm attached to the rolling means and extending downward from said rolling means to free space below the rolling means, a swing weight integral with or attached to the arm distal from the rolling means and in the free space, and measuring means located near the free space for measuring the location of the swing weight relative to the measuring means.
The apparatus may further comprise a lever attached to the rolling means for controlling the initial amplitude of the swing weight when a rolling resistance measurement is taken.
In the illustrated embodiment, the rolling means is a cylinder, and the arm extends at substantially 90xc2x0 horizontally outward from the mass center of the rolling means, and is further directed downward to a location below the rolling means, whereby the swing weight is located substantially directly below the rolling means.
The swing weight may be round or may be made having flat surfaces.
The measuring means is selected from the group comprising sound and light and the apparatus may further comprise means for collecting data from the measuring means, a computer for storing and analyzing the data, and means for outputting results.
Also provided is a method for measuring the rolling resistance of a substrate comprising the steps of (a) providing an apparatus for measuring the rolling resistance of a substrate, said apparatus comprising a rolling means for rolling contact with a surface to be measured, an arm attached to the rolling means, the arm extending downward from the rolling means to free space below the rolling means, a swing weight integral with or attached to the arm distal from the rolling means and in the free space, and measuring means located near said free space for measuring the location of the swing weight relative to the measuring means, and placing the apparatus on a substrate to be measured, (b) setting the swing weight in pendulum motion while the rolling means rolls back and forth on the substrate, (c) measuring the amplitude of the motion of the swing weight for a period of time sufficient to determine the damping rate of the substrate, and (d) correlating the damping rate of the substrate with the rolling resistance of the substrate. The method may further comprise the step of using a lever attached to the rolling means for starting the motion of the swing weight and the rolling means by holding the lever down and releasing the lever such that gravity initiates the motion and the lever controls the initial amplitude of the motion by its length.
The swing weight may be selected to be a round swing weight or a swing weight with flat sides. When a round swing weight is selected, radar is the preferred means of measuring the position of the swing weight, and when flat sides are on the swing weight, the means for measuring the position of the swing weight may be means using sound or light.
The method may further comprise the steps of (a) creating a data base of damping rates for substrates tested, (b) setting up a ranking system to correlate a damping rate with rolling resistance for a specific substrate using alpha numeric labels representative of each ranking, and (c) comparing subsequent substrates tested for rolling resistance with the ranking based on the damping rates observed for the subsequent substrates.